Fractional horsepower electric motors conventionally comprise a shell that supports a stator, end members closing the ends of the shell and bearings on the end members rotatably supporting a shaft on which a rotor is mounted. The bearings usually comprise a bearing member on the shaft which engages a seat on the end member and is yieldingly urged against the seat and an oil retainer in the form of a felt washer adjacent the bearing. In order to control end play and provide lubrication, it is conventional to provide an oil impreganted washer adjacent the bearing member, a felt washer adjacent the oil impregnated washer and an oil throw washer or slinger adjacent the felt washer which directs oil to an oil storage felt on the end member.
Such a system is intended to provide the following functions:
(1) A means of transferring oil that travels over the washer system back into the felt pack. This function is called the oil slinger and is usually accompanied by an oil slinger washer.
(2) Block the path of oil traveling down the shaft under the washers and to provide some sort of a suitable seal. A traditional method in the industry has been to use a composition Bakelite rubber material or to use an interference fit with some other plastic or metal base slinger.
(3) Provide a resilient member which is in the washer/rotor package with a function of absorbing the 120 cycle vibrations that are fundamental in the rotor assembly. These vibrations result in a clatter noise that is commonly called "end bump". Various types of material have been used--from cloth, cork, felts, to synthetic polyester materials. The basic function is to dampen vibration.
(4) Provide a bearing type surface between the rotating parts of the rotor and the stationary part of the bearing thrust surface to withstand certain frictional and thrust loads. Usually the thrust washer is oiled directly off the bearing and is made out of either steel or some of the modern plastics such as nylon.
Two of the problems that are inherent in the arrangements above are as follows:
(a) Under certain conditions it is difficult to drive the thrust washer. When the thrust washer is running against a rough bearing or dry surface, it will sometimes cause the resilient washer to slip against the thrust washer which results in a non-lubricated, non-bearing type surface which will cause a premature bearing failure.
(b) The oil slinger is generally constructed from stamped or fabricated parts and has sharp corners so that the oil, as it travels up across the surfaces, is slung off the corners in the form of droplets. It is intended that the oil travel, by virtue of its kinetic energy, across the gap into the oil reservoir. A conventional oil slinger has sharp corners and develops a fine mist with small oil droplets.
Ideally, the drops should be as large as possible in that very fine drops tend to float around in the air currents surrounding the rotor assembly and are capable of escaping complementary out of the internal oil catcher cavity and be lost forever to the oiling system. In addition, the construction should withstand the high operating temperatures which may be as high as 100.degree. C.
Among the objectives of the present invention are to provide end play and lubricating system which obviates the problems of the prior art and reduces the costs.
In accordance with the invention, the fractional horsepower electric motor comprises a stator, a shell supporting the stator, end members closing the ends of the shell, a shaft supporting a rotor within the stator, a bearing system on the end members rotatably supporting the shaft comprising a bearing member on the shaft engaging a seat on the end member, a spring means yieldingly urging the bearing member against the seat, an oil retention body associated with the bearing member, a spacer on the shaft, and a composite washer interposed between said spacer and said bearing member through which said shaft extends. The composite washer comprises a base layer of plastic filament material, a layer of elastic material bonded to one surface of the base layer, and an oil impregnated medium bonded to the other surface of the base layer and engaging said bearing member, whereby oil from the bearing passes through the base layer in capillary fashion and upon rotation is directed in small droplets toward said oil reservoir.